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United States Patent |
5,703,378
|
Shepodd
,   et al.
|
December 30, 1997
|
Materials for the scavanging of hydrogen at high temperatures
Abstract
A hydrogen getter composition comprising a double or triple bonded
hydrocarbon with a high melting point useful for removing hydrogen gas, to
partial pressures below 0.01 torr, from enclosed spaces and particularly
from vessels used for transporting or containing fluids at elevated
temperatures. The hydrogen getter compositions disclosed herein and their
reaction products will neither melt nor char at temperatures in excess of
100.degree. C. They possess significant advantages over conventional
hydrogen getters, namely low risk of fire or explosion, no requirement for
high temperature activation or operation, the ability to absorb hydrogen
even in the presence of contaminants such as water, water vapor, common
atmospheric gases and oil mists and are designed to be disposed within the
confines of the apparatus. These getter materials can be mixed with
binders, such as fluropolymers, which permit the getter material to be
fabricated into useful shapes and/or impart desirable properties such as
water repellency or impermeability to various gases.
Inventors:
|
Shepodd; Timothy J. (Livermore, CA);
Phillip; Bradley L. (Shaker Heights, OH)
|
Assignee:
|
Sandia Corporation (Alburquerque, NM)
|
Appl. No.:
|
647093 |
Filed:
|
May 9, 1996 |
Current U.S. Class: |
252/182.12 |
Intern'l Class: |
C09K 003/00 |
Field of Search: |
252/182.12
|
References Cited
U.S. Patent Documents
3896042 | Jul., 1975 | Anderson et al.
| |
3963826 | Jun., 1976 | Anderson et al.
| |
Primary Examiner: Jordan; Charles T.
Assistant Examiner: Chi; Anthony R.
Attorney, Agent or Firm: Stanley; Timothy D.
Goverment Interests
STATEMENT OF GOVERNMENT INTEREST
This invention was made with Government support under contract No.
DE-AC04-94AL8500 awarded by the U.S. Department of Energy to Sandia
Corporation for the management and operation of Sandia National
Laboratories. The Government has certain rights in the invention.
Parent Case Text
This application is a division of application Ser. No. 08/424,775, filed
Apr. 18, 1995 now U.S. Pat. No. 5,624,598.
Claims
We claim:
1. A system for removing hydrogen from an enclosed volume comprising:
a) an enclosed volume;
b) a hydrogen getter within the volume, said hydrogen getter comprising an
organic compound wherein said organic compound has the formula R.sub.x
.tbd.R'.sub.y, wherein x and y may be identical and are at least equal one
and R and R' may be identical and are benzene, styrene, naphthalene,
anthracene, biphenyl, fluorene, phenanthrene, pyrene, or alkyl substituted
derivatives or polymers thereof; and
c) a catalyst, combined with the getter, for catalyzing the reaction
between said organic compound and hydrogen.
2. The system of claim 1 wherein said enclosed volume is an apparatus for
transporting fluids comprising:
an inner tubular having an outer surface and defining an inner space
adapted for carrying fluids; and
an outer tubular disposed around said inner tubular and defining an annular
space therein.
3. The system of claim 1 wherein said enclosed volume comprises a heat
pipe.
4. The system of claim 1 wherein said enclosed volume comprises a lamp.
5. The system of claim 1 wherein said organic compound is
2-(phenylethynyl)fluorene; 2,7-bis(phenylethynyl)fluorenone;
2,7-bis(phenylethynyl)fluorene; 2,4,7-tris(phenylethynyl)fluorene;
2,4,5,7-tetrakis(phenylethynyl)fluorene;
2,3,5,6-tetrakis(phenylethynyl)-p-xylene;
1,2,4,5-tetrakis(phenylethynyl)benzene or 4,4-bis(phenylethynyl)biphenyl
and combinations thereof.
6. The system of claim 1 wherein said organic compound is
4-(9-phenanthrenenylethynyl) pyrene; trans-1,2-bis(9-anthracenyl)ethene;
or phenylethynyl substituted polystyrene and combinations thereof.
7. The system of claim 1 wherein said hydrogenation catalyst is platinum,
rhodium or palladium and combinations thereof.
8. The system of claim 7 wherein said catalyst is supported on a porous,
inert solid.
9. The system of claim 8 wherein said porous, inert solid is activated
carbon, aluminum oxide or barium carbonate and combinations thereof.
10. The system of claim 1 wherein the concentration of hydrogenation
catalyst is from about 0.1 to about 75 weight percent catalyst, wherein
said catalyst contains about 1 to 5 weight percent of a metal, based on
the weight of said catalyst.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to a method of preventing the
accumulation of hydrogen gas in enclosed spaces at elevated temperatures
and particularly to the use of organic compounds, combined with catalysts,
as hydrogen getters at elevated temperatures.
There are numerous industrial operations that require the movement of high
temperature fluids from one location to another such as heat pipes,
thermosyphons or the tubulars used in oil fields, petrochemical plants,
air separation plants and solar collectors to transport heated gases or
liquids over long distances. Because of the elevated temperatures as well
as other physical constraints inherent in these operations metal tubes or
pipes must be used. As a consequence of the outgassing or corrosion of
these metal components and thermal decomposition of the fluids transported
therein, hydrogen may be formed and accumulate with deleterious effect.
In the case of tubulars and other insulated devices, in order to maintain
the temperature of the fluid being transported the annular space between
the coaxial inner and outer tubes can be filled with an insulating
material. These insulating materials may be air or other gases or
preferably insulating fibers, powders, foams or radiative heat shields.
Significant improvements in thermal efficiency can be achieved by
evacuating the annular space. However, the accumulation of corrosion
products, particularly high conductivity gases, in the annulus causes the
thermal insulating properties of these insulated tubulars to degrade over
time.
Hydrogen, produced either by corrosion reactions between the fluid or
gases, or constituents thereof, flowing in the pipes or tubes or diffusing
in from the outside, is, because of its very high thermal conductivity, a
particular problem. The degree to which hydrogen accumulation in an
insulated tubular can degrade thermal insulating performance is well
known. It has been estimated that partial pressures of hydrogen above 0.01
torr begin to degrade thermal insulating efficiency. The thermal
conductivity of oil field tubulars utilizing an inert gas in the
insulating annulus has been known to increase by a factor of from 5-8
times over the initial values in as little as a year of service due to
accumulation of hydrogen. J. Roni et al. in "Insulated Tubular in Steam
Injection", Kawasaki Steel Technical Report, No. 16, June 1987, pp. 74-76
show that the thermal conductivity of a vacuum insulated tubular can
increase by a factor of 50 if contaminated with hydrogen.
A heat pipe works on the principle of a reflux boiler and is extremely
efficient in terms of transferring large thermal fluxes. In its
conventional form, the heat pipe is a closed tube in which a vaporizable
fluid transfers heat from an evaporation zone to a condensation zone.
Particular care is taken in the design and selection of materials of
construction of heat pipes to prevent the formation of non-condensable
gases in the pipe interior. Non-condensable gases, such as hydrogen, can
inactivate a significant portion of a heat pipe and reducing and/or
eliminating their formation from heat pipes has long been known to be of
critical importance. Although hydrogen gas formation can be prevented by
the proper selection of compatible containment and fluid materials,
economic considerations often dictate the use of low cost materials such
as carbon steel and water which generate hydrogen more rapidly.
The operating life of a lamps, either incandescent or pressured discharge
lamps, can be greatly affected by the presence of certain gases in the
internal lamp atmosphere. Water vapor is particularly harmful because even
trace amounts can cause the evaporation and redeposition in cooler parts
of the lamp of various metallic components by a process known as the
"water cycle". In an incandescent lamp, for example, the temperature of
the tungsten coil is sufficient to decompose water vapor into hydrogen and
oxygen. The resulting oxygen reacts with tungsten in the coil to form
volatile oxides which migrate to cooler parts of the lamp and condense,
principally on the glass envelope. These oxide deposits are reduced by
hydrogen to yield black metallic tungsten and reformed water, allowing the
cycle to repeat. Removing the hydrogen formed from thermal decomposition
of water vapor inside lamps by means of a hydrogen getter will prolong the
useful life of the lamp. In some lamp applications, Zr-Al getters are used
to remove hydrogen, however, these materials require a temperature in the
range of 300.degree.-400.degree. C. in order to operate efficiently. It
has long been known that hydrogen absorbing materials, known as getters,
can be used to counteract hydrogen accumulation. The use of conventional
hydrogen getter materials in insulated tubulars containing low thermal
conductivity gases to prolong the insulating properties of insulated
tubulars has been described by Perkins in U.S. Pat. No. 3,763,935. Allen
et al. discuss the use of hydrogen getters for vacuum insulated tubulars
in U.S. Pat. No. 3,720,267. Ayers et al. discuss the use of active metals
such as zirconium or titanium, and alloys thereof, for maintaining a
vacuum in the annular space in tubulars used to inject steam into an oil
well in U.S. Pat. No. 4,512,721. These metals are capable of maintaining
low hydrogen partial pressures but have the disadvantage of requiring high
temperatures for initial activation and/or ongoing operation because of
the necessity to diffuse surface contaminants into the bulk metal thereby
providing a fresh surface for continued hydrogen absorption.
Another means for removing hydrogen involves reacting the hydrogen with
oxygen to form water, in the presence of a noble metal catalyst such as
palladium, and trapping the water on a water absorbing material such as a
molecular sieve. Labaton, in U.S. Pat. No. 4,886,048, describes the use of
palladium membranes to selectively remove hydrogen from vacuum insulation
jackets such as those used in evacuated solar energy collectors where the
source of hydrogen is the thermal decomposition of a heat transfer fluid
and where a high temperature oxidizing atmosphere is available. The
conventional hydrogen getters described in the above-referenced patents
are expensive, may require special operating conditions such as high
temperature regimes or ancillary reactants in order to maintain low
hydrogen partial pressures, generally will not work well or at all in the
presence of water and/or oxygen and may pose significant safety hazards,
including fire and explosion if handled improperly, for example exposure
to air. Although many hydrogen getter materials have been described and
used in the past, particularly for insulated tubulars, this invention
discloses a new material for removing hydrogen which has significant
advantages over existing getter materials.
It is well known in the art that unsaturated carbon-carbon bonds can be
reduced by hydrogen in the presence of an appropriate catalyst to form an
alkane (see, for example, Fieser, L. F. and Fieser, M., Textbook of
Organic Chemistry, D. C. Heath & Co. 1950, pp. 66-69 and 86). This
reaction makes possible the hydrogen getters of the present invention. In
these getter systems an organic compound containing an unsaturated
carbon-carbon bond, preferably an acetylenic compound, is mixed with a
hydrogenation catalyst, typically a metal selected from group VIII of the
Periodic Table, preferably palladium, platinum or rhodium, although other
catalysts are possible, ibid. When exposed to hydrogen, the organic
reactant compound is irreversibly converted to its hydrogenated analog
with the aid of the associated catalyst, consequently the reaction can be
carried out in a vacuum and is unaffected by the presence of normal
atmospheric gases or water.
SUMMARY OF THE INVENTION
The invention disclosed herein provides a new solution to the problem of
maintaining low hydrogen partial pressures in enclosed spaces at elevated
temperatures thereby preventing the loss of performance, particularly in
heat transfer devices and piping in contact with high temperature fluids.
The organic hydrogen getter systems disclosed herein have significant
advantages over conventional hydrogen getter systems namely, low risk of
fire or explosion, no requirement for high temperature activation or
operation, the ability to absorb hydrogen even in the presence of
contaminants such as common atmospheric gases, water, water vapor and oil
mists and no requirement for the presence of ancillary gases, e.g.,
oxygen.
Accordingly, it is an object of this invention to provide a means for
efficiently removing hydrogen from enclosed spaces at elevated
temperatures, typically in excess of 100.degree. C. Another object is to
remove hydrogen from enclosed spaces where the temperature may oscillate
between low and high values. It is another object to remove hydrogen from
pipes and tubes used to transport fluids or gases at elevated temperatures
and from incandescent and pressurized lamps. A further object of this
invention to provide a novel hydrogen gettering system that has a low
vapor pressure at temperatures in excess of 100.degree. C. and which will
operate in a vacuum, in the presence of atmospheric gases or in the
presence of or in contact with water. Yet another object is to provide a
hydrogen gettering system which will not form pyrophoric or explosive
materials upon exposure to a hydrogen environment. A further object is to
provide a hydrogen getter which can be mixed with polymeric materials to
make a porous solid not wetted by water yet permeable to hydrogen. These
and other objects of the present invention may be achieved by means of an
organic hydrogen getter suitable for use at temperatures in excess of
100.degree. C., preferably from about 125.degree. C. to 200.degree. C.,
which comprises a hydrogenation catalyst mixed with an unsaturated organic
component formulated so that it and its hydrogenation products are able to
withstand exposure to hydrogen at elevated temperatures without melting or
decomposing.
Organic getter systems utilizing a catalyst to add hydrogen to a
carbon-carbon double or triple bond were first disclosed by Anderson et
al. in U.S. Pat. Nos. 3,896,042 and 3,963,826, incorporated herein by
reference. However, these prior art unsaturated precursor compounds and
their hydrogenated reaction products generally melt at temperatures below
about 100.degree. C.; the preferred operating range being
50.degree.-80.degree. C. When melting occurs organic getter materials
cease to function effectively. The surface area decreases resulting in a
precipitous decrease in the rate of hydrogen uptake. Furthermore, these
getter compounds will crosslink and char at elevated temperatures severely
degrading their effectiveness. In order to function properly at the
elevated temperatures that may be encountered, for example, while
transporting steam or high temperature liquids or in the operating
environment of a lamp, the organic reactant and its reaction product must
be chosen such that neither will be liquid nor volatile at temperatures to
which they may be exposed; temperatures which may be in excess of
100.degree. C. In the case of tubulars, the liquid formed by melting of
the organic materials can bridge the annular space between the inner and
outer tubulars creating a region of increased thermal conductivity and
reducing the insulative properties of the vacuum annulus.
The invention disclosed herein overcomes these problems by combining an
acetylenic compound having a high melting point, preferably containing at
least one phenylethynyl group, with a catalyst in a stable binder to form
a hydrogen getter such that the acetylenic reactant and its fully
hydrogenated product remain solid at temperatures above 100.degree. C. The
hydrogen getter compounds disclosed herein have the added advantage that
while they are designed to operate at temperatures in excess of
100.degree. C. they will also function effectively at lower temperatures.
Consequently, they may be employed to remove hydrogen in applications
where the temperature may oscillate between low and high temperatures,
e.g., from 0.degree. C. to 200.degree. C. and back.
Organic getter compounds are prepared by intimately mixing an unsaturated
organic reactant (alkene or acetylenic) and a suitable catalyst (typically
palladium or platinum or their dispersions on an inert support). The
getter may be manufactured as a powder or in pelletized form. When used to
remove hydrogen from tubulars, the getter must be kept from the walls of
the tubular by physical means such as by placing it between layers of
insulating cloth in order not to have an adverse effect on the heat
transfer characteristics of the annulus. Placing the getter towards the
outside of the annulus (near the cooler outer tubular wall) is preferred.
The entire arrangement is thoroughly degassed then welded shut so that the
vacuum is maintained in the annulus. The tubular is now ready to operate
and may be stored in this ready-to-use condition indefinitely. When used
in a heat pipe application where the getter will be exposed to water, the
getter may be placed in a hydrogen permeable material or pressed with a
fluoropolymer powder to make a porous solid which is not wet by water but
yet is permeable to hydrogen. In a lamp application it is preferred that
the hydrogen getter be placed in a cooler portion of the lamp and in those
instances where the lamp operates at very high temperatures, protected by
a heat shield.
The objects of the present invention together with additional objects,
novel features and advantages thereof over existing prior art forms, which
will become apparent to those skilled in the art from detailed disclosure
of the present invention as set forth hereinbelow, are accomplished by the
improvements herein described and claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 FIG. 1 shows a schematic representation of a hydrogenation reaction
in which 2,7-bis(phenylethynyl)fluorene is reduced with hydrogen in the
presence of Pd/C catalyst to 2,7-bis(2-phenylethyl)fluorene.
FIGS. 2A-2F shows examples of acetylenic compounds useful as reactants in
the hydrogenation reactions of FIG. 1:
FIG. 2A: 4,4-bis(phenylethynyl)biphenyl,
FIG. 2B: 2,7-bis(phenylethynyl)fluorene,
FIG. 2C: 2,3,5,6-tetrakis (phenylethynyl)-p-xylene,
FIG. 2D. phenylethynyl substituted polystyrene where a, b, and c are
.gtoreq.0; a+b.gtoreq.1; and the polymer chain is made up of randomly
repeating blocks of .gtoreq.0 numbers of each of these subunits in no
particular order.
FIG. 2E. 4-(9-phenanthrenylethynyl)pyrene.
FIG. 2F. trans-1,2-bis(9-anthracenyl)ethene.
DETAILED DESCRIPTION OF THE INVENTION
Hydrogenation of a carbon-carbon double or triple bond in an organic
compound by means of a catalyst (FIG. 1) is typically, an irreversible,
exothermic, heterogeneous reaction. That is, the reaction (the addition of
hydrogen to at least one unsaturated carbon-carbon bond) takes place at
the boundary between the catalyst and the organic reactant. Consequently,
in order to achieve the highest degree of effectiveness the getter
materials should preferrably be prepared using techniques that ensure that
the catalyst is in intimate contact with the active organic compound. The
preferred method is to dissolve the organic reactant in an appropriate
solvent, such as tetrahydrofuran, adding the catalyst, either as a powder
or fixed on an inert substrate such as carbon, diatomaceous earth or
asbestos or inorganic minerals or salts, evaporating the solvent and
drying the resulting powder. Getter materials may also be prepared by
melting the organic compound, mixing an appropriate catalyst with the
molten organic material and allowing the mixture to cool. The getter
material may then be converted into a powder or some other form
appropriate for its ultimate use.
The heterogeneous nature of the hydrogen getter of the present invention
causes a distribution of reaction sites that may react at different rates.
While in principle, the getter will not stop reacting until all the
unstaurated bonds have been hydrogenated, in practice, the rate becomes
vanishingly small as the getter approaches saturation. Properly formulated
getters will take up >90% of their theoretical capacity of two moles of
hydrogen gas for each triple bond in the acetylenic reactant compound
within a reasonable period of time.
Because the hydrogenation reaction can be highly exothermic, provision must
be made, in some cases, for efficient removal of the heat of reaction from
the hydrogen getter materials. Materials such as metal powders, or
preferrably excess catalyst, may be added to the getter compound to assist
in removing excess heat generated by the hydrogenation reaction. It is
preferred that the thermal conductivity of the added material be at least
0.7 Watts/cm-.degree.K
Where the getter material is exposed to or in contact with water it may be
mixed with a binder which is not wetted by water but is permeable to
hydrogen, such as a fluoropolymer powder, to make a solid. In some
instances the hydrogen getter may be exposed to gases which could
adversely affect or poison the hydrogenation catalyst, such as ammonia. In
those cases the getter material is preferably encapsulated within a
material which is impermeable to the gases which could be detrimental to
the proper functioning of the catalyst and yet permeable to hydrogen.
In order to be useful in the removal of hydrogen at elevated temperatures,
the acetylenic organic materials which are preferred for use as hydrogen
getters as well as their hydrogenation products, must be able to withstand
this rigorous environment. Generically these compounds may be represented
as R.sub.x .tbd.R'.sub.y, where x and y may be identical and may be at
least equal to one and the moieties R and R' may be identical and are aryl
or other organic groups as described herein which impart the physical
property of high melting or decomposition temperature to the precursor
materials and their hydrogenated products. The most effective compounds
are those where the moieties R and R' are stable aromatic hydrocarbons
such as benzene, styrene, naphthalene, anthracene, biphenyl, fluorene,
phenanthrene, pyrene, or an alkyl substituted derivatives or polymers
thereof. The moiety R is preferably phenyl making the substituents of R'
phenylethynyl as shown below:
##STR1##
Examples of acetylenic structures which contain the preferred
phenylethynyl structure or congeners thereof and which are useful as high
temperature hydrogen getters are shown below in FIG. 2. The acetylenic
reactant materials can be purchased commercially or synthesized from
acetylenes and halogenated aromatics using a procedure such as that
described in Havens, S.; Yu, C. C.; Draney, D and Marvel, C. S., J. Sci.
Polym. Chem. Ed., 1981, 19, 1349. These reactions usually produce
excellent yields (>90%). Compounds that require substitutions on adjacent
carbons, i.e., 1,2-dibromoaromatics usually produce lower yields (>30-80%)
of the acetylenic product.
As shown in FIG. 2, an aromatic moiety may have multiple phenylethynyl
substituents. Structures having multiple phenylethynyl groups typically
have greater capacities as measured by the amount of hydrogen that can
irreversibly react with each gram of getter. Only triple or double bonds
are considered when calculating hydrogen uptake capacity. Aromatic rings
usually do not hydrogenate except under extreme conditions of pressure and
temperature, however, certain aromatic structures such as anthracene and
phenanthrene may be readily partially hydrogenated. As an example of the
different capacities of different molecules, four preferred compounds and
their theoretical hydrogen uptake capacities are listed below.
TABLE 1
______________________________________
theoretical capacity
Compound (std cc H.sub.2 g.sup.-1)*
______________________________________
2-(phenylethynyl)fluorene
168
2,7-bis(phenylethynyl)fluorene
245
2,4,7-tris(phenylethynyl)fluorene
288
2,4,5,7-tetrakis(phenylethynyl)fluorene
316
______________________________________
*The actual capacity would be reduced by the weight percentage of the
catalyst in the final formulation.
Structures where carbon-carbon double bonds are substituted for some or all
acetylenic carbon-carbon triple bonds are also effective getters, but
suffer diminished capacity as a triple bond reacts with twice as much
hydrogen as does a double bond.
The requirements for the slurry solvent are that it: dissolve the
acetylenic compound, at temperatures below its boiling point, to produce
the desired concentration; is inert to the solute and the catalyst; and
that it is volatile enough to be vacuum stripped from the slurry in a
reasonable period of time. Many catalysts are effective when combined with
the acetylenic compounds to form the getters of this invention. Platinum,
palladium and rhodium are the most common catalysts as they function
effectively in the presence of a large number of other compounds (most
importantly; oxygen, water and carbon dioxide). Palladium, as an example,
can be used as a finely divided pure metal or as a dispersion on an inert
catalyst such as activated carbon, aluminum oxide, or barium carbonate. As
discussed earlier, vide supra, gas-solid getter hydrogenations are
heterogeneous reactions, they will only proceed if the acetylenic
compounds are intimately mixed with the catalyst. While any process that
mixes catalyst and acetylenic compound together (shaking, stirring,
grinding, blending, etc. ) will make a getter that functions effectively,
the useful capacity is proportional to the thoroughness of the mixing
process. The preferred process for formulating the getter material is to
dissolve the organic reactant in a solvent, add the catalyst to form a
slurry, remove the solvent and evaporate to dryness.
Getter formulation requires the proper concentration of catalyst for
optimum performance. Extra catalyst will speed the reaction and reduce the
capacity. Too little catalyst will increase the capacity of the getter to
absorb hydrogen, but may slow the reaction to the point where not all of
the capacity will be used. Changing the catalyst or acetylenic compound
identity requires careful evaluation of the proper catalyst concentration
to optimize reaction rates vs. the capacity needed and the cost of the
catalyst in a particular application. Preferably, 0.1-10 weight percent of
a catalyst that is 1-5 weight percent noble metal is most effective for a
wide variety of different conditions. As discussed earlier, in those
instances where the catalyst is also intended to function as a heat sink
to mediate rapid exothermic hydrogenation, the catalyst concentration may
be raised to higher values (10-75%).
EXAMPLE 1
As an example of getter preparation, 26 g of
4,4'-bis(phenylethynyl)biphenyl is added to 200-300 g of preservative-free
tetrahydrofuran that has been passed over neutral alumina to remove
potentially explosive peroxides. The catalyst, 1.1 g of 5% Pd on carbon,
is added and the three components swirled to make a gray slurry. This
slurry is heated with stirring to 50.degree.-60.degree. C. to dissolve the
biphenyl compound. The slurry is then placed on a rotary evaporator where
the tetrahydrofuran solvent is removed. Final traces of solvent are
removed from the getter using a vacuum oven (<1 ton at 75.degree. C.)
until the sample has been dried to a constant mass. The getter is a gray
powder isolated from this procedure in 100% yield.
The getter material described above was hydrogenated by exposing it to an
excess of hydrogen gas at approximately one atmosphere. The initial
hydrogenation reaction rate at room temperature was
.apprxeq.9.times.10.sup.-4 std cc H2/s g. At 120.degree. C. the initial
rate was .cent.2.times.10.sup.-2 std cc H2/s g.
EXAMPLE 2
A series of hydrogen getters was prepared exactly as in EXAMPLE 1 except
that a different solvent was used depending upon the acetylenic compound
chosen for the particular getter formulation. The acetylenic compounds and
the solvents are useful to dissolve them for subsequent formulation into
hydrogen getters are shown below:
______________________________________
Acetylenic Compound Solvent
______________________________________
2,3,5,6 tetrakis(phenylethynyl)-p-xylene
toluene
1,2,4,5 tetrakis(phenylethynyl)benzene
chloform
2,7-bis(phenylethynyl)fluorenone
acetone
2,7-bis(phenylethynyl)fluorene
methylene chloride
______________________________________
EXAMPLE 3
As an example of the ability of the getter materials disclosed herein to
function effectively when admixed with a fluoropolymer to impart water
repellancy, 2.4 g 4,4'-bis(phenylethynyl)biphenyl and 0.1 g of catalyst
which contained 5% Pd and 2.5 grams of Teflon.RTM. powder (DuPont PTFE
powder 6C) were intimately mixed and pressed into a uniform disk (7000
psi, 2 in). A portion of the disk (3.55 g) was submerged in boiling water
for about 7 hours, the heat was removed and the disk left in the water for
three days. The dripping wet sample was transferred to a reactor which was
sealed and pumped out quickly (<1 min.) to about 18 torr overgas pressure;
the sample being wet and incompletely degassed at this point. The sample
was hydrogenated in the reactor by exposure to a quantity of hydrogen
equal to 48% of its theoretical hydrogenation capacity at 1 atm. and about
90.degree. C. After eight hours, 99% of the available hydrogen had reacted
with the getter material.
From these examples, it can be seen that the objects of the present
invention are fulfilled and those skilled in the art will realize that
compounds such as phenylethynyl substituted polystyrene;
4-(9-phenanthrenenylethynyl) pyrene and
trans-1,2-bis(9-anthracenyl)ethene, FIGS. 2D, 2E and 2F, can also be used
as reactants to accomplish the objects of the present invention.
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